An X-ray diffraction analysis is available as a method for analyzing the structure of a protein molecule. A protein needs to be crystallized for the X-ray diffraction analysis, and the quality of the crystal is one important factor that governs the analysis accuracy.
Recently, it has been reported that the convection of a protein water solution can be suppressed in a microgravity environment and the quality of the protein crystal therefrom is superior than one produced in a gravity of 1 G (N. I. Wakayama, Mitsuo Ataka, Haruo Abe, “Effect of a magnetic field gradient on the crystallization of hen lysozyme,” Journal of Crystal Growth, 178 pp, 653–656, 1997).
As a method for achieving a microgravity environment for a few days, there is a method in which a sample is launched into a satellite's orbit or a method in which magnetic force is applied to a protein water solution such that the gravity is cancelled out since a protein, water, and the like are diamagnetic materials. The former method, however, has problems in that the cost is high and the opportunity is quite limited, and thus expectations are directed to the latter method in which magnetic force is utilized. Needless to say, diamagnetic material means material that is magnetized in a direction opposite to an external magnetic field H.
The present invention is directed to a device for achieving a microgravity environment by using magnetic force on Earth. The present invention is mainly applied to protein crystal growth, but not limited thereto. Thus, it can also be applied to refinement or the like of crystals other than alloys, medicine, protein, and the like utilizing a microgravity environment.
In order to virtually put a protein water solution or the like into a microgravity condition on Earth using magnetic force, there is a need for a large-absolute value and spatially-uniform magnetic force field (the product of a magnetic field and a gradient magnetic field is defined as a magnetic force field, and will hereinafter represented as a magnetic force field). At present, a large hybrid magnet that uses a superconducting magnet at the outer part and a water-cooled copper magnet at the inner part is employed as means for accomplishing a large-absolute-value magnetic force field.
Such a large hybrid magnet, however, has a magnet that is gigantic itself and also power required for the operation is as high as several mega watts. Thus, the cost for manufacturing and operating such a device becomes high.
As means for solving the problems, there are some available methods. In one method, a large magnetic force field is obtained by setting superconducting coils in a bore of a commercially-available superconducting magnet, one superconducting coil being used for generating a magnetic field in the same direction as the superconducting magnet and the other being used for generating a magnetic field in a direction opposite thereto. In another method, a ferromagnetic ring or disc is further set thereto to obtain a large magnetic force field (see Japanese Unexamined Patent Application Publication No. 2000-77225, for example).